[Beowulf]Infrastruture planning for small HPC 40/100 gigabyet eyhernet or Infiniband?

Robert G. Brown rgb at phy.duke.edu
Mon Jul 28 09:15:44 EDT 2008


On Mon, 28 Jul 2008, Eugen Leitl wrote:

> On Sun, Jul 27, 2008 at 07:19:56PM -0700, Jim Lux wrote:
>
>> bear in mind that ordinary ethernet both coax and twisted pair is
>> galvanically isolated.
>
> This is strange, because I've seen (small) sparks and received (mild)
> shocks from both, in two different locations.

Ground loop.  Very dangerous.  You go first...;-)

    rgb

>
> As you say, http://www.apcmedia.com/salestools/FLUU-5T3TLT_R1_EN.pdf
> claims Ethernet is immune, yet I've read somewhere that Gigabit ethernet
> is more susceptible than Fast Ethernet. I've got (cheap) UPSen for
> almost all equipment, maybe they're the problem and not the switching
> power supplies.
>
> In any case I'll have an electrician diagnose the problem. Unfortunately,
> I anticipate his solution would involve pulling through a new large-crossection
> ground wire to several locations. It is at this point that lack of wall
> conduits will become quite painful.
>
>

-- 
Robert G. Brown                            Phone(cell): 1-919-280-8443
Duke University Physics Dept, Box 90305
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